How can i do a matrix like this one?

Question

I was asked to type these matrices as they appear, but I don't know how to do that. (I highlighted the problem in red)

I tried so far this:

$ A= \begin{pmatrix}
 -4  &  2  & 12 \\
 2  & -6 &  9  \\
 8  &  7 & -2
 \end{pmatrix}$ \hspace{1.1cm} $ A= \begin{pmatrix}
 13  &  -21  & 9 & 12\\
 -9  & 2 &  -8 & -7 \\
 9  &  -2 & 1 & 7
 \end{pmatrix}$ \hspace{1.5cm} $ A= \begin{pmatrix}
 12  &  11  \\
 11  & 22    \\
 8  &  12 
 \end{pmatrix}$\\
 $ A= \begin{pmatrix}
 12 &  12  & -2 \\
 2  & 6 &  -9  \\
 \end{pmatrix}$ \hspace{1.3cm} $ A= \begin{pmatrix}
 -3  &  2 & 8 & 7\\
 -4  & 2 &  8 & -7 \\
 2  & -12 &  11 & 32 \\
 1  & 5 &  -21 & -12 \\
 12  & -11 &  6 & 76 \\
 11  & 12 &  -11 & -29 \\
 \end{pmatrix}$ \hspace{1.1cm} $ A= \begin{pmatrix}
 12  &  7 & 2 & 12  \\
 7  & -4 & 2 & -6 \\
 7  &  -9 & 12 & -8
 \end{pmatrix}$\\
 $ A= \begin{pmatrix}
 11 &  9  & 13 \\
 12  & -2 &  21  \\
 \end{pmatrix}$ \hspace{7.3cm}  $ A= \begin{pmatrix}
 -12  &  21 & -34 & -23  \\
 13  & -21 & 15 & 21 \\
 -43  &  16 & 32 & -19
 \end{pmatrix}$

And this was where I get.

The problem is that I have to type the code exactly as the image, but I don't see how to get that big matrix with that respective spaces.

Answer 1

It's quite hard to understand what meaning the required alignment would carry.

A three column array with nested one column arrays should do.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\[
\begin{array}{@{}l@{\hspace{1cm}}ll@{}}
\begin{array}[t]{@{}l@{}}
A= \begin{pmatrix}
 -4  &  2  & 12 \\
 2  & -6 &  9  \\
 8  &  7 & -2
\end{pmatrix}
\\
A= \begin{pmatrix}
 12 &  12  & -2 \\
 2  & 6 &  -9  \\
 \end{pmatrix}
\\[6ex]
A= \begin{pmatrix}
 11 &  9  & 13 \\
 12  & -2 &  21  \\
 \end{pmatrix}
\end{array}
&
\begin{array}[t]{@{}l@{}}
A= \begin{pmatrix}
 13  &  -21  & 9 & 12\\
 -9  & 2 &  -8 & -7 \\
 9  &  -2 & 1 & 7
 \end{pmatrix}
\\[6ex]
A= \begin{pmatrix}
 -3  &  2 & 8 & 7\\
 -4  & 2 &  8 & -7 \\
 2  & -12 &  11 & 32 \\
 1  & 5 &  -21 & -12 \\
 12  & -11 &  6 & 76 \\
 11  & 12 &  -11 & -29 \\
 \end{pmatrix}
\end{array}
&
\begin{array}[t]{@{}l@{}}
\\[-2.5ex]
A= \begin{pmatrix}
 12  &  11  \\
 11  & 22    \\
 8  &  12 
 \end{pmatrix}
\\[6ex]
A= \begin{pmatrix}
 12  &  7 & 2 & 12  \\
 7  & -4 & 2 & -6 \\
 7  &  -9 & 12 & -8
 \end{pmatrix}
\\[4.5ex]
A= \begin{pmatrix}
 -12  &  21 & -34 & -23  \\
 13  & -21 & 15 & 21 \\
 -43  &  16 & 32 & -19
 \end{pmatrix}
\end{array}
\end{array}
\]

\end{document}